Photoresist materials are commonly used in a wide number of industrial processes where it is desired to provide detailed patterns on a substrate surface in thin films applied thereto or to provide regions of altered character as contrasted to other surface portions of the substrate. Such photoresist materials are photosensitive in nature, being characterized by differential reactivity to specific liquid solvents after exposure to an energy source, such as ultraviolet radiation, for example. A standard photolithographic practice in employing photoresist layers as patterns involves the application of a layer of photoresist material to a substrate, followed by the selective exposure of the photoresist layer to an energy source, wherein portions of the photoresist layer are changed in character due to their exposure to the energy source. After such exposure, the photoresist layer is then developed by a “wet development process” employing liquid chemical solvents to selectively remove portions of the photoresist for providing the desired pattern therein.
Stripping of the patterned photoresist layer becomes necessary in most instances in the fabrication of an electronic structure after its purpose in providing a patterned mask has been served, such as for the selective application of a thin film to the underlying substrate surface or for the application of dopant materials to selected regions of the substrate, for example. Many fabrication processes for manufacturing discrete electronic devices and integrated circuits require repeated uses of photoresist layers at various stages of the process before the electronic structure is completed. Removal or stripping of each photoresist layer after it has served its purpose in the fabrication of the electronic structure is required before the additional stages in the fabrication process may be accomplished, or at least as the final stage in completing the fabrication of the electronic structure.
Many different processes have, in the past, been employed to remove exposed or unexposed portions of a photoresist layer. Unfortunately, as the industry has evolved, the processes have become problematic in certain situations. One particular situation wherein the processes have become problematic is the situation wherein an implant is implanted through an opening in a photoresist layer. For one reason or another, a hardened skin tends to form on the upper portion of the photoresist layer. The hardened skin, if not removed properly, may cause the solvent within the bulk portion of the photoresist layer to boil during the removal of the photoresist layer. Unfortunately, the boiling of the solvent tends to cause the photoresist to “pop”, coating the wafer with undesirable particle defects. These particle defects are often critical defects that lead to yield loss.
Accordingly, what is needed in the art is a method for removing a photoresist layer that does not experience the problems traditionally experienced.